The present invention relates to 1-kestose crystals and a method of producing the same.
1-kestose is a kind of so-called fructooligosaccharides which is a trioligosaccharide having fructose which forms the .beta.-1,2 bonding to the 1-position carbon atom of the fructosyl group of sucrose. 1-kestose is widely distributed in the natural world and contained in burdocks, onions and the like. A fructooligosaccharide containing 1-kestose has recently attracted attention because it has anti-cariosity and it is a bifidobacterium factor which is not digested in a human body.
There has been no existence of 1-kestose prismatic crystals with a purity of 95% or more. A known 1-kestose product is disclosed in the publication of Japanese Patent Laid-Open No. 60-149596 laid open to public in Japan. In the invention disclosed in this publication, a fructooligosaccharide solution containing 60% or more of nystose and a small amount of 1-kestose is concentrated to a solid concentration of 75 to 90%, and seed crystals containing crystal nystose are added to the concentrate obtained and dispersed therein, followed by drying, ripening and grinding to obtain a powder. The powder disclosed in the above publication contains as a main ingredient nystose and does not consist of high-purity 1-kestose crystals it self. In addition, the powder which is obtained by drying the whole syrup obtained and then grinding it contains various ingredients and no 1-kestose crystals which are isolated. The powder as a whole consists of a mixture containing three to five fructooligosaccharides
However, the above conventional powder consisting of a fructooligosaccharide mixture containing the above ingredients does not consist of complete crystals and still has hygroscopicity because it contains a plurality of fructooligosaccharides. The powder is thus inconvenient for use in its powder form in foods such as sweentener powders, convenient soup, powder juice drinks and the like, all of which are apt to be easily damaged by moisture and produced on the assumption of long-term preservation. Although it is necessary for removing the above problem to form high-purity crystals having low hygroscopicity, it is laborious to separate the three to five oligosaccharides from each other, which are contained in a fructooligosaccharide mixture solution, by using a carbon sellaite column or the like.